MR. W. C. WILLIAMSON ON THE HISTORY OF ZAMIA GIG AS. (J71 



- 1 



and from \ to f inch in diameter at the base, tapering to a point, whilst ourvin 

 outwards and upwards. 

 Pig. 1, Plate LIL, represents another specimen which exhibits additional points of 



the greatest interest. In tab. 1. fig. 2 of Young and Bird's ' Geological Survey,' t 



is o-iven a representation of a fossil from the collection of the Whitby Philosophical 

 Society, which, the Council lias permitted me to examine, along with its revei e, alio 

 in their possession. The specimen is well preserved in the centre of a block of 

 compact sandstone; but, as is so often the case with these fossils, especially where the 

 vegetable structure has been of some thickness, the friable carbonaceous matter has 



fallen away on the fracture of .the matrix, exposing the superior and interior aspects of 

 the organism. The lower surface is figured by Young and Bird ; generally it resemble* 

 the one described (fig. 2), but is somewhat smaller, the disk exclusive of the rays bein 

 only about 2 inches in diameter. The central cavity is at the same time wider and 

 shallower, being more saucer-like. Its diameter, superiorly, is about \\ inch, whilst ii 

 depth is barely f inch. At its fundus there is an irregular but well-defined eiicle, 

 | inch wide, which I believe marks the thickness of the peduncle which supported it ; 

 and from the margin of this small circular space, as from the fundus of fig. 2, numerous 



Jy marked rugee radiate towards the margin of the depressed cavity, and b 

 definite as they ascend towards its brim, where they are almost wholly lost 



Tl 



of course represent corresponding corrugations on the exterior of the organism. The 

 peripheral radii are truncated at their extremities, as represented by Young and Bird ; 

 but this is accidental, arising from their apices being imbedded in the matrix. Tie 

 Council allowed me to employ my chisel as stated above, and the result wai the display 

 of the magnificent specimen represented by fig. 1, being the cast of the superior surface 



of the organism 



Its centre is occupied by a large projecting truncated boss, on the upper surface of 

 hichis a slight depression, indicating a corresponding elevation on the surface, lnou- ■ 



few faintly developed folds 



down the sides of tbis projecting how, 



At 



there is nothing like the numerous stride seen in fig. 2. There arc, however,^,, , , „ 

 circular markings of another kind, to which I shall have to refer by-and-i>> 



base of the boss the onanism spreads out into a disk, the margin of which soppoi 



Utt °c ui me UUSJS tile urs^tUiiain op^uuo - — — # •J A . il WlV 



fifteen pointed rays ; each of these is about an ^^^^tiHLe, 



somewhat constricted at their origin, but bulge out a Mtfe Mtae -^^ ^ 



and then gradually taper off to their outer apex. Their airccuo 



tben upwards, the whole structure having **£—£ / ^mm ££ 



enmities of the rays have been curled up. Wtart 1J*«J >*£ of some of 



the form of both the upper and lower surfaces o *ese ajs 



them being retained * rite The infenor surface *«*■-* on „„. 



from side to side, the margins curling slightly downwards. The sup ^ 



other hand, has a strong ^J-£J"J £Z!Z ^oa being shown in the 



extending from the apex to about the middle of the ,nf, £~ ^ ^ rf ^ ^ 



e«t by a corresponding depression. On each *™ terminates in Ihefouil «*, 



has been concave. Where the large central depiession, , _. ^ 



VOL. XXVI. 



9 



